Electronic device manufacturers strive to produce a rich interface for users. Conventional devices use visual and auditory cues to provide feedback to a user. In some interface devices, kinesthetic feedback (such as active and resistive force feedback) and/or tactile feedback (such as vibration, texture, and heat) is also provided to the user, known collectively as “haptic feedback” or “haptic effects”. Haptic feedback can provide cues that enhance and simplify the user interface. Specifically, vibration effects, or vibrotactile haptic effects may be useful in providing cues to users of electronic devices to alert the user to specific events, or provide realistic feedback to create greater sensory immersion within a simulated or virtual environment.
Haptic feedback has also been increasingly incorporated in portable electronic devices, such as cellular telephones, personal digital assistants (“PDA”s), smartphones, portable gaming devices, and a variety of other portable electronic devices. For example, some portable gaming applications are capable of vibrating in a manner similar to control devices (e.g., joysticks, etc.) used with larger-scale gaming systems that are configured to provide haptic feedback. Additionally, devices such as cellular telephones and PDAs are capable of providing various alerts to users by way of vibrations. For example, a cellular telephone can alert a user to an incoming telephone call by vibrating. Similarly, a PDA or smartphone can alert a user to a scheduled calendar item or provide a user with a reminder for a “to do” list item or calendar appointment.
Increasingly, portable devices are moving away from physical buttons in favor of touchscreen-only interfaces. This shift allows increased flexibility, reduced parts count, and reduced dependence on failure-prone mechanical buttons and is in line with emerging trends in product design. When using the touchscreen input device, a mechanical confirmation such as pressing a button or other user interface action can be simulated with haptics.
In order to generate vibration effects, many devices utilize some type of actuator or haptic output device. Actuators used for this purpose include an electromagnetic actuator such as an Eccentric Rotating Mass (“ERM”) in which an eccentric mass is moved by a motor, a Linear Resonant Actuator (“LRA”) in which a mass attached to a spring is driven back and forth, or a “smart material” such as piezoelectric, electroactive polymers or shape memory alloys. Haptic output devices may also be devices such as electrostatic friction (“ESF”) devices or ultrasonic surface friction (“USF”) devices, or devices that induce acoustic radiation pressure with an ultrasonic haptic transducer. Other devices use a haptic substrate and a flexible or deformable surface, and devices that provide projected haptic output such as a puff of air using an air jet, etc. These actuators are able to produce strong magnitude haptic outputs. These actuators are also used to provide feedback to the user when operating a touch sensitive input of a touchscreen device.